SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e7890c16bc4a65093afef623dbccbbd4debd3c0c53f1a0f11399f31a5642ae38' 
  AND token = 'UDJNlrVcBHwvZSCfVgVXNc9BvXgn5unDBVhBhxreRRQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}